2. You may draw a visible line through the center of the lens.3. You may remove a notch from the lower quadrant of at least one lens in each pair of eyeglasses.4. You may drill a hole in each lens in the wearer's line of sight.Demonstration lenses that are devices within the meaning of section 201(h) of the act and that are offered for sale or distribution to consumers must undergo impact testing under 21 CFR 801.410.